Abstract: A method of cutting a work-piece to be cut by a laser beam, in which an incident laser beam is generated that has an initial beam parameter product (BPP), given by means of a laser source, preferably an ytterbium-doped or erbium-doped fiber laser source, coupled to at least one optical fiber for conveying the beam. Said incident laser beam is brought to a focusing head comprising at least one optical focusing device. The incident laser beam is focused by means of said optical focusing device, so as to obtain a focused laser beam, and the work-piece is cut by means of the focused laser beam. According to the invention, the quality factor of the incident laser beam is adjusted or modified by means of an optical device designed to be able to modify or vary the BPP of a laser beam so as to obtain a modified focused laser beam having a modified BPP which is different from the BPP of said incident laser beam. Associated equipment for implementing said method.

Abstract: The invention relates to method for cutting a part using a laser beam, involving the use of laser beam generation means comprising at least one ytterbium-based fibre having a wavelength of between 1 and 4 ?m in order to generate the laser beam. The laser beam is selected to have a power of less than 100 kW, a power density of at least 1 MW/cm2, a focused beam diameter of at least 0.1 mm and a quality factor (BPP) of less than 10 mm·mrad.